Arrangement for connecting a phonograph pick-up device with a radio receiving set



ag-E, Z1, 1937. i E KLQTZ Er 2,093,563

' ARRANGEMENT FOR CONNECTING A PHONOGRAPH PICK-UP DEVICE WITH A RADIO RECEIVING SET Filed Aug. 15, 1929 INVENTORS ERNST KLOTZ.

BY Emcu ZEPLER ORNEY Patented Sept. 21, 1937 Y ARRANGEMENT FOR oo'NNEoTING A PHONOGRAPH PICK-UP DEVICE 'WITH A RADIO RECEIVING SET 7 Ernst Klotz and Erich Zepler, Berlin, Germany,

, asslgnors to Telefunken Gesellschaft fiir Drahtlose Telegraphie m. b. H., Berlin, Germany, a

corporation of Germany Application August 13, 1929, Serial No. 385,664

In"Germany October 25, 1928 7 Claims.

Thisinvention relates to circuits for phonograph pickup devices. More particularlythis invention relates'to circuits for connecting phonograph pickup devices with the audio frequency amplifying stages of a radio receiving set.

It iswell known in the prior art to make a phonograph diaphragm work upon a wound magnet rather thanupo'n a horn, and to conduct the ensuing currents to a suitable point-of a receiving set, driving, for instance, a loudspeaker. In this manner, the set can be connected at will for reception by way of the antenna or to the phonograph.

According to former practice, the electric soundbox or pickup device of the phonograph has been connected withthe receiving set in such a manner that oneof the poles of the soundbox was associated with the'grid, and the other pole with the filament of the tube to be connected. In the case of a multistage receiver the tube to be thus connected is usually the one which insures the change from radio frequency to audio frequency, 1. e. the detector tube.

A ciruit illustrating the former practice and several circuits illustrating the improved arrangement according to the present invention are illustrated in the accompanying drawing in which Figure 1 is. an illustration of the former practice;

Figure 2 is an illustration of the arrangement according to this invention;

Figures 3 and 4 are modifications of the circuit illustrated by Figure 2;

Figure 5 is a detail which may be applied to the circuits; and

Figure 6 is a modification of Fig. 5.

Referring to Figure 1, r is the tube to be connected, a and b are the usual terminals for the electric soundbox of the phonograph. The grid in this scheme must therefore be united with point a by a lead. The bringing out of the grid supply lead of tube 1*, which, as stated, is usually the rectifier tube, and hence the last radio frequency and simultaneously the first audio-frequency tube of the set, is attended by the following disadvam tages:

(1) Disturbing radio frequency couplings are often set up inside the receiver by way of the said grid lead.

(2) The lead thus brought out exhibits capacity in relation to the filament, and because of the ensuing untuning of the parallel connected tuning circuit, it renders unicontrol operation of the receiver more difficult.

(3) When used in combination with a plate rectifier tube, it requires capacitive separation of the tuned circuit L, C from the grid in case of soundboX operation, because the grid would otherwise be shortcircuited for audio frequency.

(4) In the case of audion connection, the lead brought out introduces. furthermore audio frequency couplings and the picking up of audio frequency oscillations of a disturbing nature such as'line noises, etc.

In order to overcome the disadvantages cited in (1) and (4), it would be possible to provide the brought out lead with a grounded shield. But such screening means would tend to substantially increase the disturbing capacity referred to in (2), not to mention the fact that, for the usual kind of insulation material, this would inevitably occasion dielectric losses and thereby additional damping of the tuned circuit.

Now, all of these disadvantages are obviated according to the invention in which the two terminals of the soundbox are arranged at the filament end of the grid oscillation circuit.

In the embodiment Figure 2, the tuned circuit L, C is separated from the filament f, connection therewith being established by way of the terminals a, b, of the soundbox.

When operating the set for reception through the antenna these terminals are short-circuited manually or automatically. But when operating the soundbox, conditions are reversed and the soundbox of the phonograph is connected to terminals a, b.

Another scheme would be to connect between the two terminals of the soundbox, as shown in Figure 3, a regulating resistance, which, for antenna reception, short-circuits the said two points, while it is increased for soundbox operation and thus acts as a volume regulator,

Terminals a, b, as illustrated in Figure 4, could also be connected between the ends of coil L and condenser C of the tuning circuit turned towards the filament.

In all of the embodiments here described, it is recommendable to choose arrangementsso that,-

when disconnecting the soundbox, the terminals 01. and b are automatically shorted or bridged. As shown in Figure 5, this may be accomplished by means of an elastic contact connection d which, by the insertion of the soundbox pins (n, In, by the agency of an insulating piece 2 secured at the end of prong a1, is forced away from the bushing or receptacle 0., while, when the pin is Withdrawn, it is allowed to make contact again with the bush.

We claim:

1. Radio phonograph combination comprising a vacuum tube, a tuned circuit having one end connected to the grid of said tube and the other end connected to the cathode of said tube, a pair of terminals in the last mentioned connection, said terminals being adapted to be connected to the output leads of an electric reproducer, and a regulating resistance connected across said pair of terminals, said resistance being provided with a short circuiting position for radio reception.

2. A radio phonograph combination comprising a radio receiving circuit including a space discharge device, an input circuit for said device including an inductance, leads from an electric reproducer, terminals in said input circuit between one end of said inductance and the cathode of said space discharge device for connecting the electric reproducer in series with said inductance, and means for automatically short circuiting said terminals when the electric reproducer is not connected in the circuit.

3. A radio receiving set including two vacuum tubes and a transformer coupling the plate circuit of one tube with the grid circuit of a succeeding tube; means for connecting the secondary circuit of the transformer with an audio frequency circuit; a switch for opening the normal secondary circuit; and a variable condenser permanently shunting the grid circuit of the said succeeding tube, serving when the switch is closed to tune the grid circuit and when the switch is open as a tone control.

4. In a radio receiving set the combination of two vacuum tubes with their plate and grid circuits; a transformer coupling the plate circuit of the first tube with the grid circuit of the second tube, said grid circuit being grounded; a switch for opening and closing the grid circuit between the secondary of the transformer and the ground; an audio frequency circuit connected with said grid circuit at opposite sides of the switch and between the secondary of the transformer and the ground; and a variable condenser connected to ground and shunting the said grid circuit, said condenser serving when the switch is closed to tune the grid circuit and when the switch is open as a tone control.

5. A radio phonograph combination comprising a radio receiving circuit including a space discharge device, an input circuit for said device connected between the cathode and a control electrode, leads from a source of audio frequency electrical variations, means for supplying energy from said leads across said cathode and said control electrode, and a switch for short circuiting said means at times when audio frequency electrical variations are not supplied to said space discharge device and when radio frequency electrical variations are supplied thereto through said input circuit.

6. In an electron tube amplifying system, an electron tube comprising a cathode, an anode and a grid, an input circuit including a relatively high frequency input source connected between said grid and said cathode, a relatively low frequency output circuit connected between said anode and said cathode, an additional source of relatively low frequency input energy connected in said input circuit in series relationship between said high frequency input source and said cathode for independently amplifying low frequency input energy into low frequency current in said output circuit.

7. In a radio receiver, a detector tube having a cathode, an anode and a control grid, an input circuit connected between said grid and said cathode, an output circuit connected between said anode and said cathode, an electrical pick-up interposed between said input circuit and said cathode, and means for cutting out said electrical pick-up and completing said input circuit.

KLOTZ. ZEPLER. 

